Avoid Concurrent Login in ASP.NET

[cbkprasad]

Hi,

I have a critical problem regarding, avoiding the user to login to wibsite using the same credentials at the same time.The concept is once the user is logged in to application the that user credentials should be locked, i.e. no others should be able to login with that credentials....

What I have tried is with the following code
In web.Config I added following code:
<sessionState
mode="StateServer"
stateConnectionString="tcpip=127.0.0.1:42424"
sqlConnectionString="data source=127.0.0.1;user id=sa;password=letmein"
cookieless="false"
timeout="1"
/>

In Global.asax.cs:
protected void Application_PreRequestHandlerExecute(Object sender, EventArgs e)
{
// Let's write a message to show this got fired---
Response.Write("SessionID: " +Session.SessionID.ToString() + "User key: " +(string)Session["user"]);
if(Session["user"]!=null) // e.g. this is after an initial logon
{
string sKey=(string)Session["user"];
// Accessing the Cache Item extends the Sliding Expiration automatically
string sUser=(string) HttpContext.Current.Cache[sKey];
}
}

In your Login Page "Login" button handler:
private void Button1_Click(object sender, System.EventArgs e)
{
//validate your user here (Forms Auth or Database, for example)
// this could be a new "illegal" logon, so we need to check
// if these credentials are already in the Cache
string sKey=TextBox1.Text+TextBox2.Text;
string sUser=Convert.ToString(Cache[sKey]);
if (sUser==null || sUser==String.Empty){
// No Cache item, so sesion is either expired or user is new sign-on
// Set the cache item and Session hit-test for this user---
TimeSpan SessTimeOut=new TimeSpan(0,0,HttpContext.Current.Session.Timeout,0 ,0);
HttpContext.Current.Cache.Insert(sKey,sKey,null,Da teTime.MaxValue,SessTimeOut,
System.Web.Caching.CacheItemPriority.NotRemovable, null);
Session["user"]=TextBox1.Text+TextBox2.Text;
// Let them in - redirect to main page, etc.
Label1.Text="<Marquee><h1>Welcome!</h1></marquee>";

}
else
{
// cache item exists, so too bad...
Label1.Text="<Marquee><h1><font color=red>ILLEGAL LOGIN ATTEMPT!!!</font></h1></marquee>";
return;
}

}


Even though the problem is If the user closes the browser window with Alt+F4 or X button or File----> Close then the user will be kept logged.


Kindly suggest appropriate solution for this problem

Thanks and Regards,
CBK Prasad